<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script src="jquery-3.4.1.js"></script>
</head>
<style>
    div{
        background-color: red;
        width: 100px;
        height: 100px;
    }
</style>
 <body>
     <div></div>
     <button>变</button>
     <script>
         $('button').click(function(){
             $('div').animate({
                 height:300,
                 width:200
             },2000,'linear',function(){
                 alert('动画完成');
             })
         })
     </script>
     
 </body>   
</html>